Devotees defend their clay choices by saying that it has been ingested by people from across the world for hundreds of years (Shailene first learnt of eating clay from her African taxi driver), but experts say this doesn't necessarily make it advisable.

There appear to be some serious health warnings around the diet. In 2012, the Food Standards Agency (FSA), advised against ingesting clay - including bentonite.

"Exposure to arsenic can be associated with an increased risk of lung, skin and bladder cancer. Exposure to lead presents a risk for infants and children in particular, as it can be detrimental to brain development and affect intellectual performance. For the same reason, pregnant women are also advised to avoid eating or drinking clay due to the potential risk to their unborn child."

Dr. David L. Katz, a HuffPost blogger and founding director of the Prevention Research Center at Yale University, says that more work needs to be done before the clay diet can be recommended.

"Removing metal from the body is not necessarily good -- iron, for example, is a metal and essential to health. So, there could conceivably be benefits, but there could certainly be harms -- and a favorable benefit/harm ratio has not been established to justify recommending this," he told The Huffington Post.

The NHS and British Dietetic Association take issue with the detox trend as a whole.

There’s no scientific evidence to show that our bodies need help to get rid of waste products – this is what our kidneys do – and there's no proof that detox diets work

The British Dietetic Association has said that “the idea of 'detox’ is a load of nonsense. There are no pills or specific drinks, patches or lotions that can do a magic job."